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采用固相反应法制备Sm1-xCaxFeO3（x=0，0.1，0.2，0.3）样品，研究Ca2+掺杂对SmFeO3介电性能、铁磁性及磁相变温度的影响.X射线衍射图谱分析表明：所有样品的主衍射峰与SmFeO3相符合且具有良好的晶体结构.随着x的增加，SmFeO3样品的晶粒尺寸由原来的0.5 μm逐渐增大到2 μm.当f=1 kHz时，Sm1-xCaxFeO3（x=0.1，0.2，0.3）样品的εr分别是SmFeO3的5倍、3倍和2.6倍，而tg σ增大一个数量级.在3 T磁场作用下，SmFeO3样品的M-H呈线性，随着x的增加，M-H逐渐趋向饱和，Sm1-xCaxFeO3（x=0.1，0.2，0.3）样品的Mr分别是SmFeO3的20倍、31倍和68倍.X射线光电子能谱分析表明：Fe2+和Fe3+共存于Sm1-xCaxFeO3样品中，Fe2+/Fe3+比例随着x的增加而增大，证明Ca2+掺杂增加了Fe2+的含量，形成Fe2+–O2-–Fe3+超交换作用，增强SmFeO3的铁磁特性.测量了Sm1-xCaxFeO3样品在外加磁场为1000 Oe（1 Oe=79.5775 A/m）的M-T变化关系，观测到其自旋重组温度（TSR）和尼尔温度（TN）分别为438 K和687 K，发现SmFeO3样品的TSR和TN均随着x的增加向低温方向移动，当x=0.3时，自旋重组现象消失.这主要是SmFeO3样品磁结构的稳定性和Fe3+–O2-–Fe3+及Sm3+–O2-–Fe3+超交换三者共同作用的结果.In this paper we deal with the preparation of Sm1-xCaxFeO3(x=0-0.3) ceramics by the solid stat reaction and study the influences of Ca2+ doping on the dielectric,ferromagnetic properties and magnetic phase transition of SmFeO3.The crystalline structures of the Sm1-xCaxFeO3(x=0-0.3) samples are characterized by X-ray diffraction.The dielectric property is measured by a precisive impedance analyzer (HP4294A) in a frequency range from 40 to 110 MHz.The microstructures of Sm1-xCaxFeO3 are imaged with scanning electron microscope under an operating voltage of 20 kV.The coexistence of Fe3+/2+ ions in Sm1-xCaxFeO3 samples is investigated with X-ray photoelectron spectroscopy (XPS).The magnetic properties of Sm1-xCaxFeO3 are measured with the physical property measurement system.The result shows that all the peaks for Sm1-xCaxFeO3 samples can be indexed according to the crystal structure of pure SmFeO3 and their fine crystal structures are obtained by XRD.The lattice parameter a value of SmFeO3 gradually increases,while the values of b and c decrease,and the unit cell volume (V) shrinks slightly with the increase of x.The scan electron microscope images indicate that Ca2+ doping significantly increases the grain size of SmFeO3 ceramic.The average grain sizes of Sm1-xCaxFeO3 samples range from 0.5 to 2μm with Ca2+ doping.The εr values of Sm1-xCaxFeO3(x=0.1,0.2,0.3) measured at 1 kHz are about 5,3 and 2.6 times greater than that of SmFeO3,respectively,and dielectric loss increases by an order of magnitude.The increase of εr is mainly caused by the interaction between the dipole and the space charge orientation polarization.Both the conductance current and the space charge limiting current are the main factors to increase the dielectric loss.The magnetic measurements show that the M-H curves of Sm1-xCaxFeO3(x=0-0.3) samples exhibit saturated magnetic hysteresis loops with the increase of Ca2+,and the Mr values of Sm1-xCaxFeO3(x=0.1,0.2,0.3) are 20,31,and 68 times that of SmFeO3,respectively,indicating the weakly ferromagnetic behavior.The XPS spectrum indicates that the Fe2+ and Fe3+ co-exist in each of Sm1-xCaxFeO3 samples.The ratio of Fe2+/Fe3+ increases with doping Ca2+ increasing,and the magnetic preparation of SmFeO3 is enhanced.It can be attributed to the structural distortion and the formation of Fe2+–O2-–Fe3+ super-exchange.The spin recombination temperature (TSR) and the Neel temperature (TN) are obtained,respectively,to be 438 K and 687 K by measuring the M-T curves.It is noted that both TSR and TN of SmFeO3 samples move toward low temperature with the increase of x,and the spin recombination disappears when x=0.3.This is mainly due to the stability of the magnetic structure of SmFeO3 sample and the interactions of Fe3+–O2-–Fe3+ and Sm3+–O2-–Fe3+ super-exchange.
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Keywords:
- SmFeO3 /
- magnetic hysteresis loops /
- spin recombination phase transition temperature /
- antiferromagnetic phase change
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[1] Hosoya Y, Itagaki Y, Aono H, Sadaoka Y 2005 Sensor Actuat. B:Chem. 108 198.
[2] Tokunaga Y, Furukawa N, Sakai H, Taguchi Y, Arima T, Tokura Y 2009 Nat. Mater. 8 558
[3] Yuan X P, Tang Y K, Sun Y, Xu M X 2012 J. Appl. Phys. 111 053911
[4] Steele B C, Heinzel A 2001 Nature 414 345
[5] Kuo C Y, Drees Y, Fernández-Díaz M T, Zhao L, Vasylechko L, Sheptyakov D, Bell A M T, Pi T W, Lin H J, Steppke A, Tjeng L H, Hu Z, Komarek A C 2014 Phys. Rev. Lett. 113 217203
[6] Lee J H, Jeong Y K, Park J H, Oak M A, Jang H M, Son J Y, Scott J F 2011 Phys. Rev. Lett. 107 117201
[7] Yuvaraja S, Layekb S, Vidyavathyc S M, Yuvaraja S, Meyrickd D, Selvana R K 2015 Mater. Res. Bull. 72 77
[8] Xu K, Zhao W Y, Xing J J, Gu H, Ren W, Zhang J C, Cao S X 2017 J. Cryst. Growth. 467 111
[9] Zhao X Y, Zhang K L, Xu K, Man P W, Xie T, Wu A H, Ma G H, Cao S X, Su L B 2016 Solid State Commun. 231-232 43
[10] Silva-Santana M C, daSilva C A, Barrozo P, Plaza E J R, de los Santos Valladares L, Moreno N O 2016 J. Magn. Magn. Mater. 401 612
[11] Kang J, Cui X P, Fang Y F, Zhang J C 2016 Solid State Commun. 248 101
[12] Praveena K, Bharathi P, Liu H L, Varma K B R 2016 Ceram. Int. 42 13572
[13] Huízar-Félix A M, Hernández T, de la Parra S, Ibarra J, Kharisov B 2012 Powder Technol. 229 290
[14] Song G L, Su J, Zhang N, Chang F G 2015 Acta Phys. Sin. 64 247502 (in Chinese) [宋桂林, 苏健, 张娜, 常方高 2015 物理学报 64 247502]
[15] Prasad B V, Narsinga Rao G, Chen J W, Suresh Babu D 2011 Mater. Res. Bull. 46 1670
[16] Jaiswal A, Das R, Adyanthaya S, Poddar P 2011 J. Phys. Chem. C 115 2954
[17] Jung J S, Iyama A, Nakamura H, Mizumaki M, Kawamura N, Wakabayashi Y, Kimura T 2010 Phys. Rev. B 82 212403
[18] Cao S, Zhao H, Kang B J, Zhang J C, Ren W 2014 Sci. Rep 4 5960
[19] Babu P R, Bhaumik I, Ganesamoorthy S, Kalainathan S, Bhatt R, Karnal A K, Gupta P K 2016 J. Alloy. Compd. 676 313
[20] Zhang C Y, Shang M Y, Liu M L, Zhang T S, Ge L, Yuan H M, Feng S H 2016 J. Alloy. Compd. 665 152
[21] Jeong Y K, Lee J H, Ahn S J, Jang H M 2012 Solid State Commun. 152 1112
[22] Marshall L G, Cheng J G, Zhou J S, Goodenough J B, Yan J Q, Mandrus D G 2012 Phys. Rev. B 86 064417
[23] Zhao H, Cao S, Huang R, Ren W, Yuan S, Kang B, Lu B, Zhang J 2013 J. Appl. Phys. 114 113907
[24] Song G L, Zhang H X, Wang T X, Yang H G, Chang F G 2012 J. Magn. Magn. Mater. 324 2121
[25] Sati P C, Kumar M, Chhoker S 2015 Ceram. Int. 41 3227
[26] Song G L, Song Y C, Su J, Song X H, Zhang N, Wang T X, Chang F G 2017 J. Alloy. Compd. 696 503
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